Filter devices, in particular fuel/lubricant filters, are widely used in modern motor vehicles and serve for cleaning the fuels and lubricants. All usual fuels/lubricants have in common that they contain an insignificant proportion of water which, however, on the one hand, affects the fuel/lubricant with respect to its function and, on the other, increases the corrosion risk for the internal combustion engine. For this reason, a plurality of so-called water separators is already known by means of which the attempt is made to filter out or separate, as far as possible, the water content still contained in the fuel/lubricant. The higher the achievable degree of water separation, the lower is the occurring corrosion risk or the risk of an adverse effect on the function of the internal combustion engine caused by the water content.